/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineMessageInterface.h
Get the cached message and its contents for a user. Cache is populated by calling ReadMessage with a message id
pointer to message entry if found or NULL
[TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< class [FOnlineMessage](API\Plugins\OnlineSubsystem\Interfaces\FOnlineMessage) > GetMessage ( int32 LocalUserNum, const [FUniqueMessageId](API\Plugins\OnlineSubsystem\Interfaces\FUniqueMessageId) & MessageId )